The present invention relates to an electromagnetically operable pressure-regulating valve.
More particularly, it relates to an electromagnetically operable pressure-regulating valve having a magnet part with a magnet housing accommodating a magnet coil and an armature connected with a ram, and a valve connection element connected to the magnet part and having a wall provided with a duct for controlling a pressure medium and a valve seat cooperating with a valve element operable by the ram. In pressure-regulating valves of this type which are used in practice, in the pressure line leading to the pressure-regulating valve there is disposed an orifice plate. The orifice plate is usually configured in the form of an apertured orifice having a punched hole. The pressure-regulating valve which is used, for example, in automatic transmissions of motor vehicles regulates the pressure-medium current to a consumption unit in a bridge circuit with the orifice plate. A drawback in this is that dimensional and variances in dimensions and shape, resulting, for example, from wear to the punching die for the apertured orifice plate, alter the flow coefficient of the orifice plate. Consequently, the characteristic curve of the pressure-regulating valve, in particular the position and curvature thereof, is also influenced by the altered influx conditions. A further drawback is that, as the temperature falls or the oil viscosity increases, the hydraulic resistance of the orifice plate remains relatively constant. On the other hand, the laminar component of the hydraulic resistance at the valve seat in the pressure-regulating valve increases with falling temperature. These differences in resistance behavior in the event of temperature differences between the orifice plate and the valve seat lead to a variance in the characteristic curve of the pressure-regulating valve, which variance manifests itself in the so-called "residual pressure behavior". If the residual pressure is too high, this can result in operating disturbances in the consumption unit controlled by the pressure-regulating valve.